Ink jet printing has become increasingly popular as a method of producing printed advertisements, flyers and other printed media generally distributed to the public as well as printed media used in the private sector. While various ink jet printing techniques have been developed and tested, one common and reoccurring problem resides in the inability to achieve high resolution or image enhancement when using certain types of recording media especially when printing with aqueous-based inks.
Additional background including proposed solutions to the aforementioned problem is taught by Alden, U.S. Pat. No. 3,373,090; Bedell, U.S. Pat. No. 4,547,405; Jaeger, U.S. Pat. No. 4,503,111; Viola, U.S. Pat. No. 4,575,465; Viola, U.S. Pat. No. 4,592,951; IBM Technical Disclosure Bulletin, Vol. 21, No. 6, November, 1978; Japanese Pat. No. 191,083, published Nov. 24, 1982.
While the aforementioned patents and publication discuss treatment of recording media with various water-soluble polymers such as polyvinyl alcohol in order to increase the reception ability of such media to aqueous based inks, no one has previously proposed the application of a water-soluble adhesive or glue to a pre-printed recording media, i.e. a recording media such as uncoated or coated paper stock onto which an oil-based printing ink has been previously applied.
As a matter of clarification, the terminology "coated paper stock" refers to a fibrous sheet having a pigment-bearing resinous coating on one or both surfaces thereof. Usually, the pigment provides a white, bone or ivory coloration to the sheet. Most often, pigments producing a white coloration are used. The binder used in producing the coated paper stock is generally a synthetic or natural organic polymeric material. Typical binders include latices (e.g., styrene-butadiene, butadiene-acrylonitrile, etc.) film-forming polymers (e.g., polymethyl-methacrylate), and natural resins (e.g., casein, ammonium caseinate, starch, etc.). Coated paper stock generally has a gloss or semi-gloss appearance. In the advertising trade, papers having both sides coated are preferred.
When attempting to ink jet print an aqueous-based ink layer onto a recording media which has been pre-printed with an oil-based ink layer, especially a solid or uninterrupted oil-based ink layer, problems arise with regard to resolution of the aqueous ink jet printed layer. Typically, the aqueous ink jet printing will appear lighter in color and less uniformly dispersed. For example, the characters will be light and discontinuous in appearance wherein individual dots will be pronounced or discernable rather than blended together. Furthermore, the situation worsens as the thickness or density of the oil-based ink layer increases.
The foregoing problem arises due to the inability of the oil-based ink layer to properly receive and absorb or bind the aqueous-based ink. In fact, a significant percentage of the aqueous-based ink is actually repelled or deflected from the oil-based ink layer during the ink jet printing process, reducing the amount of ink which becomes deposited on the surface.
Oil-based ink printed layers are useful particularly with regard to advertising media, wherein the oil-based ink layer may contain pigments, dyes or the like in order to provide a colored zone for purposes of highlighting, etc.